This invention relates to a test head manipulator for a semiconductor integrated circuit tester with manual assist for vertical test head movement.
Certain subject matter disclosed in this application is also disclosed in U.S. Pat. Nos. 5,821,440, 6,006,616 and 6,023,173, the entire disclosure of each of which is hereby incorporated by reference herein for all purposes.
A known type of semiconductor integrated circuit tester includes a test head having an array of terminals exposed at an interface surface of the test head for engaging corresponding terminals of a load board on which a semiconductor device under test (DUT) is mounted in order to effect electrical connection between the terminals of the test head and corresponding pins of the DUT.
The tester is used in conjunction with an interfacing mechanism, such as a wafer prober or an integrated circuit device handler, for delivering semiconductor devices in succession to a test location at which an individual DUT is mounted to the load board and a test is performed. There are numerous makes and models of such interfacing mechanisms and different interfacing mechanisms have different requirements for the orientation of the DUT in the test location. A given tester should be useable with a variety of these interfacing mechanisms and it may be necessary from time to time to change the location and/or orientation of the test head. For this purpose, the test head is attached to a manipulator which permits horizontal and vertical movement of the test head and may also permit rotational movement of the test head.
When the tester is to be used with a different interfacing mechanism, the operator must carefully position the test head at the proper location and in the proper orientation to engage the load board. It is necessary to avoid collision when the test head is moved or re-oriented since this may cause damage to the test head or other equipment. Generally, a skilled and careful human operator is able to position the test head with a high degree of precision.
The moving mass of the test head may be quite substantial. It is known to use a counterbalance to support the weight of the test head and reduce the effort required to move the test head vertically upwards, but even if the weight of the counterbalance is equal to the weight of the test head, substantial forces may still be necessary to bring about vertical movement of the test head since it is necessary to overcome the inertia of rest and frictional resistance. This may make it difficult for a slightly built operator to position the test head vertically with the required degree of precision.
If the operator raises or lowers the test head by applying manual effort directly to the test head, for example by a handle attached to the test head, the height of the point of application of effort changes as the test head moves and accordingly the stance of the operator must change. This change in stance of the operator, e.g. from a stooping position to stretching upwards in an extreme case, can interfere with the operator""s ability to observe clearly the position of the test head relative to surrounding equipment and to exercise fine control over the movement of the test head, increasing the likelihood of collision.
U.S. Pat. No. 6,006,616 discloses a manipulator which includes an electric servo or other drive device to assist vertical movement of the test head and counterbalance. The servo reduces the effort required on the part of the operator to overcome the inertia of rest and frictional resistance. However, it has been found that the operator may nevertheless experience difficulty in positioning the test head vertically with the required degree of precision.
In accordance with the invention there is provided a test head manipulator for a semiconductor integrated circuit tester including a support frame, a vertical guide means attached to the support frame, a carriage mounted on the vertical guide means and movable vertically therealong, a manipulator arm attached at a proximal end to the carriage and projecting therefrom, there being a test head attached to the manipulator arm at a proximal end thereof, a counterbalance assembly mounted to the support frame for vertical movement relative thereto, a drum mounted to the support frame for rotation about a horizontal axis, a flexible tension member trained over the drum and having one end connected to the carriage and an opposite end connected to the counterbalance assembly whereby upward movement of the carriage is accompanied by downward movement of the counterbalance assembly and downward movement of the carriage is accompanied by upward movement of the counterbalance assembly, a hand operated power input element at a fixed height relative to the drum, and a force transmission mechanism which couples the power input element to the drum for transmitting manual effort from the power input element to the drum for raising or lowering the carriage.